Expand internal stop reasons.

Add explicit reasons for when a job is stopped because the real-time
clock was updated and for when a job called jobFinished() on its own
(...why did we not have this to begin with???).

Bug: 141645789
Test: atest frameworks/base/services/tests/servicestests/src/com/android/server/job
Test: atest frameworks/base/services/tests/mockingservicestests/src/com/android/server/job
Test: atest ContentResolverTest (all)
Test: atest CtsJobSchedulerTestCases
Test: atest CtsSyncManagerTest
Test: atest SyncManagerTest
Test: atest SyncOperationTest
Test: atest SyncRequestTest
Change-Id: I61392c55355d2526a32ea9597a0010b04f3875ac